Pressure-equalizing device as a prosthetic replacement for a eustachian tube

ABSTRACT

A pressure compensation device for a prosthetic substitute of a eustachian tube has an outer part and an inner part. The outer part serves for the admission of air from the outside and has a freely accessible area laterally surrounded by skin. Further, the outer part is provided with a seat for receiving a filter. This filter is accessible from the outside and keeps away coarse dirt and water. The outer part and the inner part are interconnected by a first tube. The inner part has a sealed housing divided into two chambers, namely an outer chamber communicating with the first tube and an inner chamber. These chambers are separated by either a fine filter or by a pressure compensation membrane to assure a germ tight separation. The inner chamber is connected with a second tube ending in a middle ear.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a pressure compensation device that may beimplanted as a prosthetic substitute for a eustachian tube.

Various diseases or malformations may be the cause that the middle earis not ventilated enough by the eustachian tube. Patients with chronicotitis media, chronic bone suppuration, cholesteatoma or middle earmalformations often need to have the eustachian tube replaced by acorresponding prosthesis. Said prosthesis has to assume the pressurecompensation otherwise provided by the eustachian tube. Such a pressurecompensation device is particularly necessary with middle earprostheses. Reference is made to the application of the same applicantfiled on the same date with the title “Middle ear prosthesis”. Thecontent disclosed in said application is included in the contentdisclosed in the present application.

WO-A-9310729 discloses a prosthetic substitute for the eustachian tube.It describes a ventilation tube designed as a pressure compensationdevice for the middle ear. The ventilation tube comprises outer parts,inner parts and filter parts that are tightly connected to one another.The inner part is solidly screwed into the cranial bone. The outer partis tightly screwed on the inner part. The filter part may be pluggedonto the outside located end of the outer part. The outside located sideof the filter part is provided with a filter that is air-permeable butthat is sealed against germs, water and the like, said filter beingoriented towards the outer world.

This filter part being located outside also has to prevent the middleear from getting soiled by dust, sand, water and the like. Its filtereffect is coarse in order to protect the middle ear against infectionsby germs. In order to be able to protect it against water and germpenetration, the filter part has to be extremely fine pored. Due to theoutside location of the filter part, the very fine pored filter runshigh risks to get obstructed by coarse particles such as dirt or dust.

The object of the present invention is to provide a pressurecompensation device that replaces the natural eustachian tube whenlatter is not able to ventilate the middle ear, whereas simultaneouslythe service life of the filters used and the sterility of a possiblechange of filter are to be improved.

The solution of this object is to provide a pressure compensation deviceas a prosthetic substitute for a eustachian tube with an outer part andan inner part that are tightly connected via a first tube, whereas theouter part 1. may be anchored in a bone and has a freely accessible areacompared with the surrounding skin, 2. has a seat for a filter beingaccessible from the outside and 3. is provided with an inside connectionfor the first tube and whereas the inner part has a sealed housingdivided into two chambers, namely into an outer chamber and an innerchamber separated from each other either by a fine filter or by apressure compensation membrane, the outer chamber communicating with thefirst tube via a connection and the inner chamber being connected via aconnection with a second tube ending in the middle ear.

Thanks to the pressure compensation device according to the invention,the ventilation of the eardrum, that is of the middle ear, from a headarea accessible from the outside is possible. To that purpose, the outerpart is inserted into the bone and is laterally surrounded by skin sothat it projects outwards, being thus accessible from the outside. Thetechnique used therefor is quite similar to the one used for boneimplanted hearing aids. The outer part is preferably arranged behind theear and covered as best as possible by the ear concha.

The outer part serves for the admission of air as well as for keepingaway coarse dirt and water from the other parts of the pressurecompensation device. It is therefore equipped with a filter located in aseat of the outer part and is preferably exchangeable.

The outer part is connected to the inner part via the first tube. Thefunction of the inner part is to assure a germ-tight separation. Theinner part has a housing divided into two chambers. These two chambersare either separated from each other by a highly flexible but totallyimpermeable membrane or they are connected to each other via a finefilter. The two chambers of the housing are designated as outer chamberand as inner chamber, the outer chamber being connected to the outerpart via the first tube. The inner chamber is connected with the middleear via the second tube, preferably with a middle ear prosthesisprovided there.

The highly flexible membrane sees to it that no germs coming from theouter chamber may enter the inner chamber. The fine filter has the samefunction, said filter being additionally air-permeable. In order toprovide the fine filter with the biggest possible filter surface, thefilter is preferably designed as a hollow fiber filter. With regard tohollow fiber filters overall, reference is made to the U.S. Pat. Nos.5,108,464 and 5,002,590 and particularly to the literature cited there.

The use of two filters (coarse and fine filter) as claimed in thepresent invention and more particularly the use of a coarse filter andof a highly elastic membrane protecting the middle ear against dirt andinfections has considerable advantages compared with the filterarrangement in pressure compensation devices of the art:

1. The coarse filter located outside is susceptible to obstruction. Itmay be reached from the outside and is easily exchangeable.

2. The extremely fine pored fine filter arranged in the inner part runshigh risks of obstruction by dirt. It is protected against dirt by thecoarse filter arranged on the outer part. The obstruction of the finefilter is thus reliably prevented by the outside located coarse filter.The fine filter needs no more to be changed. If, instead of the finefilter, a highly flexible membrane is used for pressure compensation,the problems occurring by obstruction and described above are entirelyavoided.

3. The arrangement of the fine filter inside the inner part implanted inthe cranial bone protects the fine filter against any mechanicalinfluence and thus against damage.

4. The outer part is connected to the inner part by means of a tube andsaid inner part is connected to the middle ear by means of another tube.This is of great cosmetic advantage. The tubes and the inner part may beimplanted in the cranial bone so as not to be visible from the outside.The outer part may be freely positioned and more particularly implantedso as not to be visible from the outside.

5. As already explained under 2., the separation of coarse and finefilter increases the service life of the fine filter which has no moreto be exchanged. When changing the coarse filter, which has to be donefrom time to time, the fine filter or the membrane always prevent germsto penetrate into the middle ear. As opposed to the pressurecompensation devices of the art, the pressure compensation deviceaccording to the invention guarantees sterility during a possible changeof filter.

Further advantages and characteristics of the invention will becomeclear in the remaining claims and in the following description ofembodiments that are only examples and are not limiting the scope of theinvention. Said embodiments are explained in more detail with the aid ofthe drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: is a sectional side view of a middle ear prosthesis with thepressure compensation device according to the invention, the pressurecompensation device being provided with a highly flexible membrane,

FIG. 2: is a representation of the pressure compensation deviceaccording to FIG. 1, but now with a fine filter in the inner part and

FIG. 3: a sectional representation of an inner part equipped with hollowfibers serving as fine filter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 a pressure compensation device is represented together with amiddle ear prosthesis. Both are described in the following:

The middle ear prosthesis has an artificial eardrum 20 with anessentially oval blank. Its surface is bigger than the surface of anormal human eardrum and is for example 1.5 times bigger. It is made ofa material biologically appropriate to the use as a prosthesis.

The eardrum 20 is tightly connected to a housing consisting in twoparts. The connection is more precisely achieved by means of atransmission part 22. Said transmission part has essentially the shapeof a tube. It has a cylindrical area represented in the lower part ofFIG. 1 and an area expanding from said cylindrical area and running onan envelope of cone. The diameter of the cylindrical area is ofapproximately 6 mm. The expanding area has corresponding measurements ofabout 11 mm. As may be seen in FIG. 1, the eardrum 20 is located on onelevel and runs in an angle of 37° to a longitudinal axis 23 of thetransmission part 22. Due to the slant position of the eardrum 20, theeardrum 20 has a bigger surface than the normal ear.

A second ossicle part 24 is durably fastened on the inner side of theeardrum 20, preferably in the center of the surface. In the presentembodiment, a commercial ossicle substitute of the enterprise RichardsGmbH is used. It has a ball-and-socket joint in the vicinity of theeardrum 20. Underneath said ball-and-socket joint a hollow shankreceives a first ossicle part that still has to be discussed. The secondossicle part 24 runs underneath the ball-and-socket joint centrically tothe center line of the transmission part 22.

The housing also has a coupling part 28. As a whole it is a bit smallerthan the transmission part 22 and is designed together with saidtransmission part in such a way that both parts may be interconnected inan easy, tight and durable way, whereas the interconnection particularlyoccurs by plugging in longitudinal direction and by gluing. The couplingpart 28 is essentially cylindrical. Its diameter is also ofapproximately 6 mm. It has a free end area 30 having a course imitatingas accurately as possible the individual relief of the eardrum wall of awearer of the middle ear prosthesis. As already explained above, severalprocedures are available to scan or detect the course of the individualrelief of the eardrum wall. Reference is also made in this connection tothe patent application “Device for the mechanical scanning and detectionof the course of the eardrum wall in a middle ear” of the same applicantand with the same filing date. The disclosure content of thisapplication is included into the disclosure content of the presentapplication.

The free end area 30 is accordingly designed so as to sit close to theeardrum wall 32, as may be seen in FIG. 1. A hermetically sealed closuremay thus be obtained at that place. In order to carry through theconnection between the free end area 30 and the eardrum wall 32, liquidfastening and sealing material may be used.

In the coupling part 28 a holding device 34 is provided for the firstossicle part 26. Said ossicle part 26 is designed as a thin golden wirethat closely fits through a very small, artificial opening 36 in astapes base plate 38 and that is projecting with its lower, free endarea into the inner ear 40. In the embodiment shown, the holding device34 is an essentially slantways running wire onto which the first ossiclepart 26 is fastened or may be fastened. During implantation of themiddle ear prosthesis, the holding device 34 is cut through so that thefirst ossicle part 26 which is connected to the second ossicle part 24may move freely back and forth through the holding device.

In the embodiment of the middle ear prosthesis as it is shown here, theinner space has to be accessible in order to connect the two ossicleparts 24, 26 and to cut through the holding device 34. Other embodimentswithout such an access are also possible. A window 42 is provided in thetransmission part 22 for said access, whereas the window may be closedby a cover plate 44.

As is shown in FIG. 1, the cover plate 44 has a connection 52. It isassigned for a tube 54. The tube 54 is leading to an inner part of apressure compensation device. Said inner part 56 is designed as aboxlike housing with two chambers, namely an outer chamber 58 and aninner chamber 60. Both are hermetically separated from one another by avery flexible membrane 62. In another embodiment they are separated fromone another by a fine filter 63 that is impermeable to bacteria andmicrobes, but permeable to air. The fine filters 63 particularly usedare hollow fiber filters, see FIG. 3.

The outer chamber 58 is connected to an outer part 66 via another tube64. It is anchored in a bone 76 and is partially accessible from theoutside, see skin 78. The construction used here is similar to the oneused in so-called bone-conductive hearing aids. The outer part 66 has arecess 68 into which a filter 70 is inserted. Said filter is preferablyexchangeable. The filter 70 hinders water, coarse dirt and so on topermeate into the tube 64. The barrier against germs and the like isachieved by the membrane 62 or by the fine filter replacing it.

In the embodiment shown in the FIGS. 2 and 3, the inner part is notprovided with a highly flexible membrane 62. The two chambers 58, 60 areseparated from one another by a fine filter 63. Said filter is sodesigned that no germs may permeate from the outer chamber 58 into theinner chamber 64.

Since, after insertion of the prosthesis according to the invention, theinner part is no longer directly accessible and may only be accessed toby another surgical intervention, great importance is attached to themechanical are for example permanent. The housing of the inner part ispermanently hermetically closed. The membrane 62 has a very highresistance. The same is true for the fine filter 63.

FIG. 3 shows an inner part in the housing of which a big number ofhollow fibers 90 is arranged. Together they are constituting the finefilter. They are essentially running parallel to one another. They mayalso sit close to each other, since their circular shape anywayguarantees free spaces between the different hollow fibers. In therepresentation shown, the free spaces are pertaining to the innerchamber 60. The inner chamber may alternatively also be connected to theinner spaces of the hollow fibers 90. In the drawing according to FIG. 3the spaces between the different hollow fibers are big in order for thedrawing to be better readable. If the hollow fibers 90 should not toucheach other, the spacing between them should be kept as small aspossible.

FIG. 3 shows that around all the hollow fibers 90 a plug is cast attheir left end side so that a free access to their inner spaces is givenfrom the left. The plug 92 tightly coats each of the hollow fibers inthe area of their outer sheath and tightly seals the inner wall of thehousing.

At its right end side, each and every one of the hollow fibers 90 isclosed, for example by dipping it into a corresponding, liquid plasticor by squeezing. In the drawing, this closure is represented bydifferent stoppers 94. They assure that each and every one of the hollowfibers is hermetically closed at its right end side (in FIG. 3).

Membranes for hollow fibers of the type discussed above are known out ofthe U.S. Pat. No. 4,781,733 as well as of the prior art cited.

What is claimed is:
 1. A prosthetic eustachian tube replacing oneincapable of fully ventilating a middle ear impaired by disease ormalformation, or to ventiltate a middle ear prosthesis, said eustachiantube replacement prosthesis comprising an accessible outer part and apermanently sealed inner part, the outer part being adapted to beanchored in a bone so as to be accessible from outside and partlycovered by skin, a filter seat in said accessible outer part, aninterchangeable filter means in said filter seat to protect saidpermanently sealed inner part from water and dirt, said permanentlysealed inner part being in the form of a hermetically closed housingadapted for implantation, said housing being divided into two chambers,an air-permeable, but germ-tight means separating the two chambers intoa first and second chamber, permitting air flow from the first chamberto the second chamber while restricting the penetration of bacteria andmicrobes into the second chamber, tube means connecting the accessibleouter part and the first chamber of the permanently sealed inner part topermit air flow therebetween, and tube means connecting the secondchamber of the permanently sealed inner part with the middle ear topermit air to ventilate said middle ear.
 2. The prosthetic eustachiantube according to claim 1, characterized in that the tubes are designedas silicone tubes.
 3. The prosthetic eustachian tube according to claim1, characterized in that the pressure compensation membrane is a thin,tight and highly flexible foil.
 4. The prosthetic eustachian tubeaccording to claim 1, characterized in that the housing is essentiallyboxlike.
 5. The prosthetic eustachian tube according to claim 1, whereinthe germ-tight means separating the two chambers is a fine filter. 6.The prosthetic eustachian tube according to claim 1, wherein thegerm-tight means separating the two chambers is an impermeable membrane.7. A pressure compensation device for a prosthetic eustachian tube, saiddevice having an outer part and an inner part tightly connected by afirst tube, the outer part having a means for anchoring it in a bone andfor surrounding it by skin, permitting it to serve for admission of airfrom outside, the inner part having a means for implanting it in amiddle ear, said outer part having a seat for receiving a filter, whichfilter blocks coarse dirt and water, said inner part having a sealedhousing divided into two chambers, namely into an outer chamber and aninner chamber separated from each other in a germ-tight manner by a finefilter or by a pressure compensation membrane, the outer chambercommunicating with the first tube and the inner chamber communicatingwith a second tube ending in the middle ear.
 8. A pressure compensationdevice for a prosthetic eustachian tube, said device having an outerpart and an inner part tightly connected by a first tube, the outer parthaving a means for anchoring it in a bone and for surrounding it byskin, permitting it to serve for admission of air from outside, saidouter part having a seat for receiving a filter, which filter blockscoarse dirt and water, said inner part having a sealed housing dividedinto two chambers, namely into an outer chamber and an inner chamberseparated from each other in a germ-tight manner by a fine filter or bya pressure compensation membrane, the outer chamber communicating withthe first tube and the inner chamber communicating with a second tubeending in the middle ear, the inner chamber having its fine filter madeof a plurality of hollow fibers, which essentially run parallel to oneanother, which have essentially the same lengths, and which have aclosure means at one side end that closes each of the fibers with theother end being tightly encompassed by a plug.